I am going to install engineered wood flooring on a floor that is currently covered with plastic laminate. Plywood, then wood subfloor is under the laminate. Do I need to remove the laminate before installing the wood floor?

First of all why wouldn't you remove the laminate? It only takes about 3 minutes.

It is glued down and it does not come up easily.

Then it is not a plastic laminate. They are all floating floors, you must have vinyl. How are you going to install the wood? Nail down, floating, or glue down? I am assuming nail down. If it is laminate that someone decided to glue down(don't know why) rip it up, if it is vinyl then you can nail through it, make sure you don't have any height problems if your going to go over it.

Wilsonart had a glue down laminate type installation years ago. What a nightmare that was.

You might be correct, sounds vaguely familiar. On a side night Wilsonart is pulling out of the flooring business on 12/03/10.

It is vinyl. We are going to nail down the wood. How far should the nails penetrate the plywood beneath the vinyl.

Check with the manufacturer the installation instructions should tee you what type of fasteners to use.